The disclosure relates to a method for operating a braking system of a motor vehicle, wherein the braking system comprises at least one hydraulically actuable wheel brake, a brake actuation device for hydraulically actuating the wheel brake, an electric brake booster for setting a predefinable hydraulic braking boost and at least one parking brake assembly associated, in particular, with the respective wheel brake.
The disclosure further relates to a device for operating a braking system which carries out the above-described method, and a corresponding braking system having such a device.
Methods, devices and braking systems of the type mentioned in the introduction are known from the prior art. Conventional braking systems in motor vehicles operate hydraulically a driver generating a hydraulic pressure by actuating a brake actuation device, in particular a brake pedal, which pressure is generated, in particular, by means of a brake master cylinder and is transmitted by means of a plurality of valves to one or more wheel brakes of the motor vehicle. With valves switched appropriately, the hydraulic pressure acts on a brake piston of the respective wheel brake in order to displace said brake piston to generate a clamping force between brake linings and brake disk. To assist the driver it is also known to provide a brake booster which makes available a braking boost in dependence on the actuating force exerted on the brake pedal by the driver, which boost raises the hydraulic pressure beyond that which the driver introduces into the braking system solely by actuating the brake pedal. High braking forces can thereby be generated, even if the driver is able to exert only a low braking or actuating force. Such a brake booster is usually in the form of a vacuum brake booster, as disclosed, for example, in the unexamined patent application DE 199 50 029 A1.
However, systems are known by now in which the brake booster is in the form of an electric brake booster. Such a braking system is disclosed, for example, in the unexamined patent application DE 10 2009 000 769 A1. In this case the braking boost is set independently of the actual actuation of the brake pedal by activation of an electric actuator of the brake booster. In addition, it is known from the aforementioned document to change the hydraulic braking boost made available by the brake booster in dependence on an operating situation of the motor vehicle.
It is also known to associate a parking brake assembly with the respective wheel brake. In particular, it is known to integrate the parking brake assembly into the wheel brake in such a way that the parking brake assembly has a separate actuator which nevertheless acts directly or indirectly on the elements of the wheel brake already present, such as, in particular, brake pistons, brake pads and brake disk. A distinction must therefore be made between a service brake, which is activated hydraulically by the driver by means of the brake actuation device and if applicable by the brake booster, and the parking brake assembly which is integrated in the service brake assembly.